We are studying the physiologic interaction between the retina and the retinal pigment epithelium (RPE). The purpose of this work is to increase our knowledge of ocular and visual physiology, and to deal more effectively with diseases of the eye which involve the RPE. Several physiologic processes are under investigation. First the mechanisms of adhesion between the retina and RPE, and the mechanisms for the resorption of sub-retinal fluid, are being investigated with experimental models. These allow the direct measurement of the force required to peel retina from the wall of the eye, and monitoring in vivo of the rate of fluid resorption from local experimental detachments. Second, electrical responses to light which involve the RPE (c-wave and standing potential) are being studied to analyse the source, significance and interaction of these slow potentials. This work is being applied to the development of clinical tests for human use, such as the d.c.ERG, which will hopefully provide clinical information about RPE function.